The present invention relates to an apparatus for mixing liquids in a certain ratio, and more particularly to an apparatus, for exampie, for mixing a deionized water and a hydrofluoric acid precisely in the ratio of 100:1, so as to produce mixtures which are properly used in etching wafers.
General)y, in order to prevent poor wafer etching in manufacturing semiconductor products, deionized water and hydrofluoric acid should be mixed in a predetermined ratio, for exampie, precisely in the ratio of 100:1. Referring to FIG. 1, there is shown an example of a conventional mixing apparatus. In the mixing apparatus, predetermined amount of deionized water and hydrofluoric acid are introduced in a buffer tank 33 through liquid f)ow meters 31 and respective)y, so that the aleionized water and the hydrofluoric acid are mixed in the ratio of 100:1 therein. Then, the resulting mixture pumped into a chemical bath 35 by means of a chemical pump 34.
In the convent)oral mixing apparatus, however, the volumes of the deionized water and the hydrofluoric acid are not precisely measured, so that the mixture ratio deviates from a desired ratio by about 2%. As a result, the etching of wafers is deteriorated.